Week 2 - Understanding Burden and Severity of Respiratory Infections

Question 1

How do we use surveillance data for severity assessment?

Answer 1

Determine influenza activity thresholds in routine data to characterize the severity of the current and previous influenza seasons (and pandemics)

Question 2

How do we use surveillance data in understanding disease burden?

Answer 2

Estimate national disease burden (# illnesses, hospitalizations, deaths, etc.) annually using data available during season

Question 3

What is a severity assessment?

Answer 3

Assessment needed to inform a scale of response
Looking at the
- Impact on the population
- Transmission
- Seriousness of illness

Question 4

What is the Preliminary Assessment?

Answer 4

Provide a broad assessment of the relative transmissibility and clinical severity
Can identify prevention and control measures in well-characterized early outbreaks

Question 5

Preliminary Assessment: Framework

Answer 5

A: Low- Moderate severity & Low- Moderate transmissibility
Estimated to be similar to the range seen in annual seasonal epidemics

B: Low- Moderate severity & Moderate - High Transmissibility
Transmission is greater than seasonal epidemics. Prepare for disruption from absenteeism and outpatient services.

C: Moderate - High severity & Low- Moderate transmissibility
Transmission is similar, though severity is greater than seasonal epidemics. Prepare critical health systems.

D: Moderate - High Severity & Moderate - High Transmissibility
Transmission and severity greater than annual seasonal epidemics. Control transmission to limit severe illness; prepare for demand on critical health systems.

Question 6

What is the refined assessment?

Answer 6

Activity accelerates and more data are captured in enhanced surveillance systems ( e.g., line list, case reports ), and special studies ( e.g., FF100, school/community outbreaks ).

Increased confidence/precision in measures of transmission and severity

Early decisions can begin to be revised if indicated

Question 7

What is the Ongoing Assessment?

Answer 7

Activity is epidemic nationwide and data are captured in routine surveillance systems.
Monitor the progression of the epidemic and capacity to manage the burden in the population
Scale up or scale down interventions as needed
as the epidemic progresses

Question 8

Challenges to Understanding Disease Burden

Answer 8

• Not everyone seeks medical care
• Complications can be broader than respiratory illness
• Surveillance not conducted everywhere
• Symptoms similar among respiratory pathogens
• Illnesses not often confirmed with laboratory testing
• Many adults no longer shedding virus when tested
• Pathogen rarely recorded on death certificates

Question 9

Lessons Learned

Answer 9

Integration w/ existing workflows,
infrastructure; ongoing preparation during
seasons is key

Combined work across surveillance, special
studies, communications

Match message to audience; simple key
messages are most useful
– Know your stakeholders
– What questions are they trying to answer?